1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device wherein defect of withstand voltage deterioration caused by chipping or cracks from the dicing region side can be reduced and there is no need to apply etching removal of the measurement electrode after the inline inspection.
2. Background Art
A power semiconductor device such as an IGBT (Insulated Gate Bipolar Transistor), diode, power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) and the like is a semiconductor device controlling large electric power unlike the other semiconductor devices such as a memory, a microcomputer and the like. In these power semiconductor devices, reduction of a power loss which is a sum of a steady loss in a device ON state and a switching loss at switching is in demand. In response to that, optimization of a device design dimension in silicon has been meeting the market request.
As a surface electrode of the power semiconductor device, a thick film electrode having a thickness of 1.0 μm or more is made of aluminum. This is to prevent an increase in the steady loss caused by spreading resistance of an electrode portion during a large-current operation. Moreover, a thin film barrier metal (TiN, TiW and the like) is formed under the aluminum similarly to the memory, the microcomputer and the like. As a result, diffusion of aluminum over the silicon surface is prevented, and diffusion of silicon into aluminum is prevented. Moreover, by forming a silicide layer, contact resistance between the electrode and the silicon is reduced, and variation of the contact resistance is reduced and made stable.
At the same time as the surface electrode of the power semiconductor device, a surface electrode for an inline inspection monitor arranged on a dicing region is also formed. The inline inspection monitor is an inspection pattern for inspecting whether or not a device pattern is being normally formed in a production line. Abnormality in a production process is detected by making film thickness measurement or dimension measurement in middle processes during a wafer process. Moreover, by feeding back a result to a production condition depending on the case, stable production with reduced variations in manufacture is realized.
In addition, there is an inline inspection monitor for measuring sheet resistance, contact resistance, inverted voltage or the like of an impurity diffusion layer of a P type semiconductor and an N type semiconductor in silicon after completion of the wafer process. These inline inspection monitors are not formed in a power chip region used as a product but are formed in an ineffective region such as a dicing region, a wafer outer periphery or the like.
The surface electrode of the power semiconductor and an electrode of the inline inspection monitor measurement are formed at the same time. Since aluminum in the surface electrode of the power semiconductor device is a thick film of 1.0 μm or more, aluminum of the monitor measurement electrode is also formed as a thick film. Since the monitor is located on the dicing region, during a dicing process, thick film aluminum of the monitor measurement electrode needs to be cut at the same time as silicon or an oxide film to be diced. In the dicing using a general dicing blade, a wafer is cut by cutting work using a dicing blade rotating at a high speed. However, since soft and highly ductile aluminum has poor cutting performance, biting of aluminum into an uneven part of the dicing blade can easily occur depending on the pressure of the dicing blade during dicing. The bitten aluminum gives a local stress different from original dicing to silicon in irregularity on a silicon cut surface by means of rotation of the dicing blade, and chipping (chips) or cracking (cracks) might be caused in silicon. If the chipping and cracks reach a withstand-voltage holding part of an edge termination portion in a power chip, it causes withstand voltage failure in a final product inspection process (final test) conducted in a last process of power module assembling, which might deteriorate a yield.
Thus, in order to suppress chipping or cracks caused by dicing, a manufacturing method is proposed (see Japanese Patent-Laid-Open No. 2001-308036, for example) in which only metal of the electrode for measuring the inline inspection monitor located on the dicing region is removed by etching treatment after inline inspection, and then, dicing is performed.